1. Field of the Invention
The present invention generally relates to a photosensitive drum of an image forming apparatus and method of damping vibration in the drum. More particularly, the present invention relates to a photosensitive drum of an image forming apparatus with a structurally improved vibration damper for damping vibration of the photosensitive drum and a method thereof.
2. Description of the Related Art
Generally, an electrophotographic image forming apparatus is used in a printer, a copier, a facsimile, each of which is provided with a photosensitive drum.
The photosensitive drum is composed of a cylindrical drum which is made of a conductive material and has an outer surface onto which a photoconductive material is coated. When a light source emits light with image information toward the photosensitive drum, the physical properties of the applied photoconductive material are changed. Thereby, an electrostatic latent image is formed on the photosensitive drum.
The photosensitive drum resonates due to vibration from the gears of the motor rotating the photosensitive drum. The photosensitive drum is also vibrated due to friction when it contacts a cleaning blade which removes developer remaining on the photosensitive drum so a new electrostatic latent image can be formed.
The vibration of the photosensitive drum causes its rotation speed to fluctuate, so that the photosensitive drum cannot correctly receive the image information from the light source, thereby deteriorating the image quality.
Further, the vibration of the photosensitive drum is transferred to its neighboring units and casing, thereby causing unwanted noise.
To overcome the above problems caused by the vibration of the photosensitive drum, the prior art has proposed installing a vibration damper in the photosensitive drum to dampen the vibrations from the photosensitive drum. Such an example has been disclosed in Japanese Patent Publication No. 2001-235971 (entitled “PHOTOSENSITIVE DRUM AND METHOD OF DAMPING VIBRATION THEREOF”), the entire enclosure of which is incorporated herein by reference.
As for its configuration, a photosensitive drum is provided therein with a metallic cylinder. The metallic cylinder is at least partially surrounded by an elastic member on its outer circumferential surface. The elastic member on the outer circumferential surface of the metallic cylinder is brought into close contact with the vibration damper, which has a coating. The vibration damper is disposed in the cylinder to absorb the vibration of the photosensitive drum.
Another example has been disclosed in Japanese Patent Publication No. 1993-188839 (entitled “IMAGE FORMING APPARATUS”), the entire enclosure of which is incorporated herein by reference.
As for its configuration, a core member is inserted in a photosensitive drum, wherein the core member is constructed by dispersing particles onto an elastic member. The dispersed particles are heavier than the elastic member. The elastic member is heavier than the photosensitive drum and has a predetermined hardness.
However, in the conventional vibration damping configurations disclosed in Japanese Patent Publication Nos. 2001-235971 and 1993-188839, it is very troublesome to insert the vibration damper into the photosensitive drum, while in close contact with the interior of the photosensitive drum. Furthermore, when the photosensitive drum is relatively thin in thickness, there is a possibility of deforming the photosensitive drum.
Furthermore, such a photosensitive drum is expensive to manufacture and is difficult to disassemble after initially being assembled.
FIG. 1 is a perspective view of a conventional configuration where a vibration damper is provided outside of the photosensitive drum.
Referring to FIG. 1, a wheel balance 5 is provided on a rotation shaft 3 of the photosensitive drum 1, wherein the wheel balance 5 is provided outside the photosensitive drum 1, takes a disc shape and has a diameter lager than that of the photosensitive drum 1.
In this manner, when the wheel balance 1 is provided outside the photosensitive drum 1, a separate additional space is needed for installation of the wheel balance 1. Further, its material cost is quite high.